A position sensor is a device that can detect the presence and location of a touch that results from a user's finger or some other object such as a stylus. In some instances, a position sensor is overlaid on a display screen; and the sensor detects touches within the display area. In a touch sensitive display application, the position sensor allows a user to interact directly with what is displayed on the screen, rather than indirectly with the displayed objects by using a mouse or touchpad. By way of example, position sensors can be attached to or provided as part of computers, personal digital assistants (PDA), satellite navigation devices, mobile telephones, portable media players, portable game consoles, public information kiosks, automatic teller machines (ATMs) and point of sale systems. Position sensors have also been used as control panels on various appliances.
There are a number of different types of position sensors that are used as part of a touch screen. Examples include, but are not limited to, resistive touch screens, surface acoustic wave touch screens, and capacitive touch screens. A capacitive touch screen, for example, may include an insulator coated with a transparent conductor in a particular pattern. An object, such as a user's finger or a stylus, that touches or is brought into close proximity to the surface of the screen causes a detectable change in capacitance. This change in capacitance is sensed and its location can be determined by a controller that processes the detected change in capacitance.
In many applications, the touch screen and associated circuitry can detect a touch gesture as well as a touch at a particular location. Detection of a gesture can be determined by monitoring multiple touches over time. In recent years, touch sensitive position sensors have been used in mobile devices, which often have two touch screens that slide apart or flip open like a book. The two or more screens can function together as a single larger touch screen. In these two-screen devices, detection of a gesture across the gap between the two screens is lost. Thus, the gesture will not be tracked as a single gesture. The loss of detection results in the gesture being interpreted as a separate gesture on each of the screens.